In the past, straw was not considered a suitable structural material. Unlike wood, straw has not been considered for its strength and has not commonly been considered as a building material. Current trends in the use of straw for construction involve straw bales where dense packing and size provide necessary strength and structural support. In fact, in many countries, the use of straw for construction is not permitted due to a common conception that straw is a poor building material.
In the description that follows the term cereal straw is to encompass other lignocellulosic material that is cereal straw-like in structure, such as rice straw and bamboo. Heretofore a thin panel of compressed non-woody lignocellulosic material (i.e. straw) has been made by mixing short straw pieces with a binder. Disclosure of this thin panel is found in U.S. Pat. No. 5,498,469 in the name of Howard et al. issued Mar. 12, 1996, incorporated herein by reference. The panel is used as a core layer or core stock in a plywood laminate; thus a thin layer of straw panel, is sandwiched between two layers or sheets of plywood. Although this thin panel .about.0.10 inches appears to perform its intended function, the thin panels do not have sufficient strength as structural boards. The panels were incorporated with stronger wood laminate layers for the production of plywood.
Other references relating to fiber panel methods of manufacture and devices for making such panels are: U.S. Pat. No. 5,730,830 in the name of Hall, issued Mar. 24, 1998; U.S. Pat. No. 5,729,936 in the name of Maxwell, issued Mar. 24, 1998; and, U.S. Pat. No. 5,728,269 in the name of Kohno et al., issued Mar. 17, 1998.
It is an object of this invention, to provide a structural board that does not require expensive laminations forming wood/straw composites.
It is an object of this invention to provide a structural board comprised of straw and having a strength that far exceeds the strength of the straw panel described by Howard et al.
In accordance with this invention, a board or panel is provided wherein the majority of strands of straw are substantially oriented in a parallel fashion. The strands are combined with a binder.
In accordance with another aspect of the invention a board is provided wherein strands of straw are oriented in a predetermined fashion or wherein at least straw strands within at least a layer are oriented in a substantially predetermined fashion.
In accordance with the invention, there is provided, a panel, board, or beam, comprising:
a compressed straw elongate material having a plurality of strands, a plurality of the strands being substantially split longitudinally to allow a binder to contact some of the inside of the strands; and binder for binding the straw into a solid panel, board or beam. PA1 a compressed straw elongate material having a plurality of split strands, a plurality of the split strands being oriented in a predetermined manner; and PA1 isocyanate binder for binding the straw into a solid panel, board or beam. PA1 providing a plurality of strands of cereal straw; PA1 splitting the cereal straw; PA1 orienting the cereal straw such that a plurality of strands are substantially parallel; and, PA1 adding binder to the cereal straw. PA1 a core of: PA1 outer layers comprised of compressed strands of lignocellulose material other than straw.
In accordance with the invention, a panel, board, or beam, is provided comprising:
In accordance with another aspect of the invention, there is provided, a method of fabricating a panel, board or beam comprising:
In accordance with the invention, there is provided, a panel, board, or beam, comprising:
a compressed straw elongate material having a plurality of strands, a plurality of the strands being substantially split to allow a binder to contact some of the inside of the strands; and PA2 binder for binding the straw into a solid panel, board or beam; and,
In accordance with the invention a device for splitting straw is provided comprising two closely spaced shear rollers, said rollers being substantially the same size and having a diameter of substantially about 200 mm-800 mm.
In accordance with yet another aspect of the invention, a straw panel is provided bonded with MDI (DiphenylMethane Diisocyanate) resin and preferably, wherein a DPMA (DipropyleneGlycolMonomethylEtherAcetate) extender is used.
The strands preferably have a length of about 10 mm or greater, and preferably, are 50-100 mm long.
Structural, board, beams or panels can be fabricated in accordance with the teachings of this invention.